frontend\modules\topic\models\Topic::beforeSave PHP Method

    public function beforeSave($insert)
    {
        if (parent::beforeSave($insert)) {
            if ($this->tags) {
                $this->addTags(explode(',', $this->tags));
            }
            $this->content = TopicService::contentTopic($this->content, $this) . ($this->cc ? t('app', 'cc {username}', ['username' => Yii::$app->user->identity->username]) : '');
            if ($insert) {
                $this->user_id = $this->user_id ?: Yii::$app->user->id;
                $this->type = self::TYPE;
                $this->last_comment_time = $this->created_at;
            }
            return true;
        } else {
            return false;
        }
    }